1. Field of the Invention
This invention relates to ball valves, and more particularly to ball valves controlling the flow of a high temperature abrasive fluid-particulate mixture.
2. Description of the Prior Art
In processes where valves are used to control flow of an abrasive fluid medium, particularly at high temperatures, there is a tendency to rapidly erode valve interior components and the valve body. This is particularly evident in processes for treating coal or other hydrocarbonaceous materials, such as coal gasification and liquefaction systems.
For example, it was found that high temperature, stainless steel ball valves experienced a useful life limited to 35 to 50 hours when used in the inlet piping of a demonstration coal gasification unit. This piping transported particulate coal and/or char in a transport gas, such as recycled product gas, at a temperature of approximately 110.degree. C. The erosion occurred at the valve body interior, both at the inlet and outlet, as well as at the valve ball.
It is thus desirable to provide an improved valve which is not as susceptible to erosive degradation. Preferably the improved valve should require only minimum modification, not utilize exotic, expensive materials, and substantially extend the valve useful life.